Process of reacting partially swollen cotton textiles with aqueous solutions of specific aldehydes containing acid catalysts to produce wet and dry crease resistance



United States Patent Office 3,046,079 Patented July 24, 1962 Anon-exclusive, irrevocable, royalty-free license in the invention hereindescribed, throughout the world for all purposes of the United StatesGovernment, with the power to grant sublicenses for suchpurposes, ishereby granted to the Government of the United States of America.

This invention relates to an improved process for the treatment ofcotton textiles with formaldehyde.

The processes that have been known heretofore are not satisfactory foruse on cotton textiles because of the great loss of strength that isbrought about. An object of the present invention is to provide aprocess for reacting formaldehyde with cotton textiles without excessivereduction of the strength of the cotton fiber or fibrous product.Another object of the present invention is to provide an improvedpractical process for producing cotton textiles which are relativelynon-shrinkable and which have a high degree of dry and wet wrinklerecovery, and which at the same time have good tearing and tensilestrengths. Still another object of this invention is to producecrossliuked cotton textiles with the above named properties which havemoisture regain values of about 7% or greater.

To achieve the object of this invention the cotton textiles is allowedto steep in .a solution containing water, a water-soluble organicliquid, formaldehyde, and a mineral acid catalyst under such conditionsthat the reaction of formaldehyde with the cotton textile reaches thedesired stage. To stop the reaction at the desired stage the cottontextile is washed free of unreacted formaldehyde and acid or the acid isneutralized with a suitable base before drying it.

In carrying out the process of this invention the proportion of water towater-soluble organic liquid is the factor which determines to a largeextent the final properties of the product. The proportion of water towatersoluble liquid must be such that the cotton cellulose is not in afully swollen state, but in a partially swollen state. The proportion ofwater should range about from 8% to 40%, based on the weight of thesolution. It is also very important that the cotton fiber is not in acompletely dry condition at the time it is reacted with theformaldehyde. Therefore, itis necessary to have sufficient water-solubleorganic liquid present to prevent the complete swelling which would beobtained if the system were entirely aqueous. The preferred proportionof water-soluble organic liquid lies in the range of about 50% to 90%based on the total weight of the solution, including water,water-soluble organic liquid, formaldehyde, and mineral acid.

The rate of reaction of formaldehyde with the cotton cellulose dependson the concentration of mineral acid and formaldehyde in the treatingsolution and upon temperature. The concentration of formaldehyde andmineral acid can be varied over a considerable range, but relatively lowconcentrations of mineral acid (1%- 17.2%) and formaldehyde (1%-10%)have been found to be adequate. The temperature at which the reaction iscarried out will also affect the rate of reaction of formaldehyde withthe cotton cellulose. The time required decreases rapidly with anincrease in temperature.

' The reaction may be carried out at temperatures ranging from slightlyabove the freezing point of the solution to about 45 C. The preferablerange is about 25 C. to 35 C. The strength of the modified cottontextile is greatly reduced at temperatures substantially above C. Thetime of reaction may be varied from about 3 minutes to several hours,the longer times generally being required at the lower temperatures.

After the reaction has been carried to the desired stage it is desirableto wash the product thoroughly to free it of unreacted formaldehyde and'acid. At some stage during the washing it is preferable to add in analkaline substance such as sodium carbonate to the wash water toneutralize the acids.

The cotton textiles processed according to this invention may be in theform of loose fibers, yarns, or fabrics. The cotton textiles may beprocessed on existing textile machinery such as a jig or J-Box, or theymay be processed by festooning. The type of equipment used forprocessing is not an important feature of this invention. The processusing the jig is preferred for fabric. When the process is carried outat the higher temperatures the reaction proceeds at such a rate that acontinuous process may be used. Yarn can be readily treated according tothis invention in a package dye machine. Aldehydes other thanformaldehyde which react with cellulose to crosslink it may be used inthis process. Such aldehydes include glyoxal, glutaraldehyde,adipaldehyde, and 0&- hydroxy adipaldehyde, acetaldehyde andbenzaldehyde. Aldehyde derivatives, such as dimethylol ethylene urea mayalso be used.

Water-soluble solvents useful in this invention are organic compoundswhich have relatively little (as compared to water) or no swellingaction on cotton cellulose fibers. extent of at least 5%. Examples ofuseful water-soluble liquids are: acetone, dioxane, diethylene glycol,dimethyl ether, tetrahydrofurane, organic acids such as acetic, formic,propionic, and lactic acids. Mixtures of organic compounds such asbenzene in acetic acid and xylene in tetrahydrofurane are usefulliquids. With these mixtures it is important that water will dissolve inthem to the extent of at least 5% of the weight of the mixture. Aceticacid is the preferred water soluble organic liquid for use in thisinvention.

Catalysts suitable for use in this invention include mineral acids ofthe group consisting of hydrochloric acid, sulfuric acid, and phosphoricacid. The reaction rate is greatest at a particular temperature andreagent concentration when hydrochloric acid is used.

The products obtained by the process described herein have excellent wetand dry crease resistance. Both of Water must be soluble in theseliquids to the these qualities are necessary for a fabric if the fabricis to dry smooth and unwrinkled after Washing and tumble drying. Whencotton fabrics or fibers are reacted with formaldehyde and an acidcatalyst by the drying and curing process, they have good wet and drycrease recovery, but suffer a great loss in strength. In addition, thereproducibility of the process is diflicult and not practical. Anadvantage of the process of this invention is the greater tear andtensile strength retention of the product. This improved strengthretention is made possible by allowing the reaction of formaldehyde withcotton to take place while the cellulosic material is Wet with thetreating solution at a temperature not exceeding 45 C., and is in apartially swollen state. Temperatures much above 45 C. destroy thestrength of the cotton. For example, at a temperature of 75 C., over 75%of the strength of cotton is lost in about 5 minutes, whereas thestrength of regenerated cellulose is not greatly affected at the highertemperatures. Another advantage of the process is that various degreesof dry crease recovery can be obtained merely by changing theconcentration of water in the solutions. At the lower concentrations ofWater (8% to 30%) excellent dry crease recovery as well as excellent wetcrease recovery can be obtained. As the water concentration is increasedthe dry crease recovery of fabric products show less improvement overthe control, and finally with over about 50% water in the system noimprovement at all is obtained in dry crease recovery, although the wetcrease recovery is still very good. An object of this invention is toproduce cotton fabrics with good wet and dry crease recovery. It isevident that properties of the final fabric product are dependent on thedegree of fiber swelling at the time the reaction takes place, which inturn are determined by the amount of water present. For instance, cottonfabric soaked for 5 days in a solution containing 3.6% formaldehyde,3.7% hydrochloric acid, and 92.7% water contained only 0.4% combinedformaldehyde, and had no improvement in dry crease recovery. Bone drycotton fabric soaked for 5 days in an anhydrous solution containing thesame concentrations of formaldehyde and hydrogen chloride (the remainderbeing acetic acid) contained combined formaldehyde but was extremelydegraded, the fabric retaining only about 15% of its original strength.On the other hand, cotton fabric soaked for only one hour in a solutioncontaining 3.6% formaldehyde, 3.7% hydrochloric acid, 17.7% water, and75% acetic acid contained 0.8l.0% combined formaldehyde and hadexcellent wet and dry crease recovery, and about 70% strength retention.This again illustrates the advantage of carrying out the reaction withinspecified limits of water concentration.

Softening agents such as silicones, polyethylene, polyacrylonitrile, orlong chain fatty acid derivatives may be used to improve the strength,abrasion resistance and hand of the product. Up to 90% Elmendorf tearingstrength retention has been obtained by this process by using a softeneras an after treatment. The softeners may also be applied to the fabricsbefore treating with formaldehyde.

Cotton fabrics produced by this process have the quality of dryingsmooth after repeated laundering whether they are drip-dried,line-dried, or tumble-dried. Other properties such as fiber density,moisture regain, water of inhibition, and dyeability are affected by thetreatment. For example, moisture regain of treated fabrics was generallygreater than that of the untreated fabrics.

changed is again dependent on the degree of fiber swell- The extent towhich these properties are ing at the time the reaction of formaldehydewith the cellulose takes place.

The following examples illustrate the methods of carrying out theinvention but the invention is not restricted to these examples. Treatedfabrics were tested by the standard methods of the American Society forTesting Materials, Philadelphia. Breaking strength was determined by theone inch strip method, tearing strength by the Elmendorf method, and drycrease recovery by the Monsanto method. Wet crease recovery was carriedout by first thoroughly wetting the sample with water, blotting, andthen measuring the crease recovery of the wet sample by the Monsantomethod. The percentages are by weight.

EXAMPLE 1 A series of solutions was prepared containing varying amountsof formaldehyde, hydrochloric acid, water, and acetic acid. Thecomposition of these solutions are shown in Table I.

Table I Calculated Amount of Acetic Acetic Solution No. Water in ECHO,H01, Acid, Anhy- Final Percent Percent Percent dride, Solution, PercentPercent 1 1 The amount of water indicated includes a small amount ofmethanol which was in the formaldehyde as a stabilizer.

2 The percent acetic acid here do s not include that formed from thereaction of Water and acetic anhydride.

The solutions were prepared by mixing glacial acetic acid, 36% aqueousformaldehyde, and 37% hydrochloric acid in the ratio required to givethe desired concentrations. In some of the solutions containing a highconcentration of water, it Was necessary to add water in addition tothat present in the formaldehyde and hydrochloride acid to obtain thedesired water concentration. In some of the solutions containing lowconcentrations of water, it was necessary to add enough acetic anhydrideto react with a portion of the water in the formaldehyde andhydrochloric acid to obtain the desired Water concentration.

The water concentration in the series was varied from 92.7% (where noacetic acid was used) to 0.0% (where only acetic acid was used as thesolvent). The concentration of formaldehyde was varied from 3.6% to7.5%, and that of the hydrochloric acid from 3.7% to 17.2%.

Several samples of bleached unmercerized cotton print cloth wereimmersed in each solution. A sample was. removed from each solution attime intervals varying from 3 minutes to 6 hours in the more reactivesolutions and up to 5 days in the less reactive solutions. All of thereactions were carried out by allowing the samples to steep in thesolutions at room temperature (about 27 C.). After the samples of fabrichad been removed from the reaction media, they were washed thoroughlywith water to remove unreacted formaldehyde and acids. The amount ofcombined formaldehyde in the cotton was determined, as well as physicalproperties such as wet and dry crease recovery and tearing strength. Theproperties of some of these samples are shown in Table II.

Table II.-Physical Properties Formaldehyde Treated Bleached Cotton PrintCloth Physical Properties at various times and solution concentrationsReaction Time, Grease Recovery Hrs. Combined Tearing Angle MoistureECHO, Strength (Warp Fill) Regain, Percent (Warp) Percent gnis.

Dry Wet SOLUTION NO. 2

SOLUTION NO. 5

SOLUTION NO. 7

SOLUTION NO. 8

SOLUTION NO. 9

CONTROL (UNTREATED PRINT CLOTH) The data shows that after two or threehours reaction time in solution No. 2 there is not much improvement inthe dry crease recovery even at the higher formaldehyde and hydrochloricacid concentrations. This was due to the high degree of swelling in thecompletely aqueous system. The dry crease recovery began to increase asthe water concentration was reduced. Good wet crease recovery was alsoobtained. Moisture regain values varied from about 7.0% to about 9.4%.The moisture regain of the untreated fabric was 6.7%. In this experimentoptimum fabric properties were obtained when using solutions 5 through8, at water concentrations of 30% to 12.6%. Print cloth reacted for twohours in solution No. 4, contained 1.84% combined formaldehyde and haddry crease recovery angle of 249 and a wet angle 360. Bone dry printcloth reacted for 3 days in solution No. 10 contained only 0.17%combined formaldehyde and had a dry crease recovery angle of only 156and a wet crease recovery angle of only 180; the tearing strength wasonly 215 grams. The disadvantage of using a completely aqueous orcompletely anhydrous system is readily apparent if good wet and drycrease recovery and good strength are desired.

Print cloth was also reacted at time intervals of 3, 10, and minutes inthe solutions of Table I. This cloth had formaldehyde contents varyingfrom 0.25% to .75% and had wet and dry crease recovery.

EXAMPLE 2 A series of solutions were prepared containing 3.6%formaldehyde, 3.0% hydrochloric acid, 16.4% water,

and 77% acetic acid. Samples of bleached print cloth, bleachedbroadcloth, and mercen'zed bleached print cloth were steeped in thesesolutions at temperatures varying from about 20 C. to about 45 C. attime intervals varying from 5 minutes to 90 minutes. After the sampleswere allowed to react for the required length of time they were removedfrom the solut ons and washed thoroughly with water to remove unreactedformaldehyde and acids. The amount of combined formaldehyde wasdetermined as well as tearing strength and wet and dry crease recoveryangles. The results of some of these tests are shown in Table III. Theadvantage of using mercerized fabric is evident from the greaterstrength retained.

Table III.The Efiecr of Temperature and Time on Properties ofFormaldehyde Treated Cotton Fabrics Wrinkle Recovery Tem- Time, Com-Tearing Angle Cotton Fabric, pera- Minbined Strength (Warp Type ture,utes H OH 0, (Warp), Fill) 0. Percent gms.

Dry Wet;

20 30 0. 57 465 210 232 20 90 1.10 315 257 290 35 5 0. 50 500 232 244Bleached print 35 10 0. 68 490 244 274 cloth 35 30 1. 06 340 262 302 455 0. 84 360 258 278 45 10 1. 10 325 277 298 45 20 1. 36 255 280 303 0.72 805 232 204 Mercerized print 25 6O 1. 02 670 249 288 cloth 10 0.71760 228 287 35 30 1. 29 620 262 313 10 1. 26 655 265 209 Bleached broad-35 10 0.72 360 248 302 cloth 45 5 0. 85 350 269 305 Untreated control,bleached print cloth 1,050 188 152 Mercerized control, print cloth...1,150 195 199 Untreated control, bleached broadcloth 950 184 204 EXAMPLE3 A pilot plant run was carried out as follows:

A solution was prepared containing 2,140 ml. of 37% aqueousformaldehyde, 2,380 m1. of 36% hydrochloric acid, and 17,780 ml. ofglacial acetic acid. The solution contained about 3.7% formaldehyde,3.6% hydrochloric acid, 12.1% water, and 80.6% acetic acid. A piece ofbroadcloth, print cloth, and mercerized print cloth were sewed togethermaking a total of yards of 18" width fabric. The fabric was treated withthe solution for one hour at room temperature (about 27 C.) using a jig.The reaction was stopped by first washing the fabric in water containingsodium carbonate, and then rinsing well with cold water, and finallywith hot water and drying on a tenter. Best results were obtained on themercerized print cloth, which had a formaldehyde content of 1.12%, a drycrease recovery angle of 250", a wet crease recovery angle of 300, and atearing strength of 630 grams. The tearing strength was increased to 800grams by applying 0.3 to 0.4% polyethylene softener to the treatedfabric. This was a 75% strength retention based on the bleached controlfabric and a strength retention based on the mercerized control fabric.

EXAMPLE 4 A pilot plant run was carried out as follows: A solution wasprepared containing 2,132 ml. of 36% aqueous formaldehyde, 2,378 ml. of37% hydrochloric acid, 13,742 ml. of acetic acid, and 3,138 ml. ofacetic anhydride. The acetic anhydride reacted with a portion of thewater to give a solution containing 3.6% formaldehyde, 3.7% hydrochloricacid, 10.0% water, and 82.7% acetic acid.

Fifty yards of fabric (consisting of 20 yards of bleached print cloth,12 yards of mercerized print cloth, and bleached broadcloth) weretreated with this solution in the same manner described in Example 3.Best results were obtained on the mercerized print cloth, which had aformaldehyde content of 0.96%, a dry crease recovery angle of 260, a wetcrease recovery angle of 280, a tearing strength of 785 grams, and abreaking strength of 32 lbs. After 1% of a silicone softener was appliedto the treated mercerized print cloth, it had tearing strength of 940grams and a breaking strength of 36.3 lbs. This was a 95% tearingstrength retention and a 70% breaking strength retention based on theunmercerized control. This also was an 87% tearing strength retentionand a 64% breaking strength retention based on the mercerized control.

EXAMPLE A solution was prepared containing 3.6% formaldehyde, 9.4%sulfuric acid, 17.7% water and 69.3% acetic acid. A piece of bleachedcotton print cloth was immersed in the solution for 1 hour at roomtemperature (about 27 C.). The fabric was then removed from the solutionand washed free of unreacted formaldehyde and acids, and dried. Thefabric contained 1.94% formaldehyde, and had a dry crease recovery angleof 275 and a wet crease recovery angle of 269.

EXAMPLE 6 A solution was prepared containing 3.6% formaldehyde, 2.9%hydrochloric acid, 16.9% water, and 76.6% acetic acid. A piec ofmercerized cotton print cloth Was immersed in the solution for 1 hourand then removed and washed thoroughly with water. The fabric contained0.94% formaldehyde, had a dry crease recovery of 244, a wet creaserecovery of 288, and a breaking strength of 36.5 lbs. Th breakingstrength of the mercerized control fabric was 52.4 lbs. The treatedfabric retained 70% of its breaking strength. The treated fabric wassubjected to home launderings using a detergent. The dry crease recoverywas then 232, and the wet crease recovery was 273. The fabric lost only5% of its crease recovery. The breaking strength after the 20launderings was 40.4 lbs.a 77% strength retention based on themercerized control fabric.

EXAMPLE 7 Each of four samples of mercerized cotton broadcloth wastreated with a difierent softening and/ or water repelling agent. Theseagents were (1) a 1% aqueous solution of Saparnine WL (acid salt of acomplex amino organic compound), (2) a 1% solution of Sapamine WLfollowed by the application of a 3% aqueous emulsion of Zelan AP, (3) a1% aqueous emulsion of Primenit VS (N,N-octadecyl ethylene urea), (4) a1% aqueous emulsion of a silicone. Each of these agents was applied to asample of fabric by standard procedures. Then each softened or waterrepellent sample was immersed in a solution equivalent to solution No. 7in Table I of Example I, and allowed to react for one hour at roomtemperature (27 C.). The samples were removed and washed free of excessformaldehyde and acid. The wet and dry crease recovery angles using thedifferent softening and water repelling agents are shown in Table IV.

Silicone 324 288 We claim: 1. A process comprising steeping a cottontextile in a solution containing, based on the weight of the solution,

about from 50% to of an organic water-soluble liquid in which water issoluble to the extent of at least 5% and selected from the groupconsisting of acetone, dioxane, diethylene glycol, dimethyl ether,tetrahydrofurane, formic acid, acetic acid, propionic acid, lactic acid,a mixture of benzene in acetic acid, and a mixture of xylene intctrahydrofurane, about from 1% to 10% of an aldehyde selected from thegroup consisting of formaldehyde, glyoxal, 'glutaraldehyde,adipaldehyde, a-hydroxy adipaldehyde, acetaldehyde, and benzaldehyde,about from 8% to 40% of water, and about from 1% to 17.2% of a mineralacid catalyst selected from the group consisting of hydrochloric acid,sulfuric acid, and phosphoric acid at a temperature not exceeding about45 C. to partially swell and react the cotton cellulose with thealdehyde, and removing all steeping solution from the thus-treatedcotton textile to obtain a modified cotton textile characterized in thatit has a combined aldehyde content of at least 0.25% based on the weightof the textile, a moisture regain value of at least 7% based on theweight of the textile, a breaking strength of at least 50% of theoriginal untreated textile, and possessing both wet and dry wrinklerecovery.

2. The process of claim 1 wherein the organic watersoluble liquid isacetic acid.

3. The process of claim 1 wherein the aldehyde is formaldehyde.

4. The process of claim 1 wherein the mineral acid catalyst ishydrochloric acid.

5. The process of claim 1 wherein the temperature ranges about from 20C. to 45 C.

6. A process comprising steeping a cotton textile in a solutioncontaining, based on the weight of the solution, about from 50% to 90%of acetic acid, about from 1% to 10% of formaldehyde, about from 8% to40% of water, and about from 1% to 17.2% of hydrochloric acid at atemperature of about from 20 C. to 45 C. to partially swell and reactthe cotton cellulose with the formaldehyde, 'and washing thethus-steeped cotton textile free from the steeping solution with waterto obtain a modified cotton textile characterized in that it has acombined formaldehyde content of at least 0.25% based on the weight ofthe textile, a moisture regain value of at least 7 based on the weight"of the textile, a breaking strength of at least 50% of the originaluntreated textile, and possessing both wet and dry wrinkle recovery.

References Cited in the file of this patent UNITED STATES PATENTSSchappel May 25, 1954 OTHER REFERENCES

1. A PROCESS COMPRISING STEEPING A COTTON TEXTILE IN A SOLUTIONCONTAINING, BASED ON THE WEIGHT OF THE SOLUTION, ABOUT FROM 50% TO 90%OF AN ORGANIC WATER-SOLUBLE LIQUID IN WHICH WATER IS SOLUBLE TO THEEXTENT OF AT LEAST 5% AND SELECTED FROM THE GROUP CONSISTING OF ACETONE,DIOXANE, DIETHYLENE GLYCOL, DIMETHYL ETHER, TETRAHYDROFURANE, FORMICACID, ACETIC ACID, PROPIONIC ACID, LACTIC ACID, A MIXTURE OF BENZENE INACETIC ACID, AND A MIXTURE OF XYLENE IN TETRAHYDROFURANE, ABOUT FROM 1%TO 10% OF AN ALDEHYDE SELECTED FROM THE GROUP CONSISTING OFFORMALDEHYDE, GLYOXAL, GLUTARALDEHYDE, ADIPALDEHYDE, A-HYDROXYADIPALDEHYDE, ACETALDEHYDE, AND BENZALDEHYDE, ABOUT FROM 8% TO 40% OFWATER, AND ABOUT FROM 1% TO 17.2% OF A MINERAL ACID CATALYST SELECTEDFROM THE GROUP CONSISTING OF HYDROCHLORIC ACID, SULFURIC ACID, ANDPHOSPHORIC ACID AT A TEMPERATURE NOT EXCEEDING ABOUT 45*C. TO PARTIALLYSWELL AND REACT THE COTTON CELLULOSE WITH THE ALDEHYDE, AND REMOVING ALLSTEEPING SOLUTION FROM THE THUS-TREATED COTTON TEXTILE TO OBTAIN AMODIFIED COTTON TEXTILE CHARACTERIZED IN THAT IT HAS A COMBINED ALDEHYDECONTENT OF AT LEAST 0.25% BASED ON THE WEIGHT OF THE TEXTILE, A MOISTUREREGAIN VALUE OF AT LEAST 7% BASED ON THE WEIGHT OF THE TEXTILE, ABREAKING STRENGTH OF AT LEAST 50% OF THE ORIGINAL UNTREATED TEXTILE, ANDPOSSESSING BOTH WET AND DRY WRINKLE RECOVERY.